This invention relates to an ignition timing control method and apparatus for internal combustion engines, especially to a so-called "time control system" ignition timing control method and apparatus. In such controls, the ignition spark advance is determined (in angular measure, expressed in degrees) from the operating status of the engine and used to calculate a time, which is measured from a cylinder reference point determined for each cylinder to establish a measurement ending point at which ignition occurs (the "ignition point").
In the time control system internal combustion engine ignition timing controller described in Japanese Patent Laid-Open No. 83452/1990 and No. 140463/1990, for example, a crank angle sensor generates a pulse whose leading edge is a predetermined distance before top of dead center (B.T.D.C.). At this point a spark advance value is determined based on engine speed, and a time period which corresponds to the spark advance value is calculated and measured from the leading edge of the pulse in order to locate the ignition point. In such an arrangement, however, if the engine speed changes after measurement is started at the leading edge of the pulse, the ignition timing is also changed, and the time of the power supply to the ignition coil becomes too long or too short.
The same problem also arises in connection with fuel injection control, since the same sensor output pulses are used.
The purpose of this invention, therefore, is to reduce the error that is caused by engine speed changes in engine timing control devices such as described above. The control method and apparatus according to the invention can also be applied to fuel injection controllers.
Another purpose of this invention is to supply a sensor which may be used with such a control method and apparatus.